Shift mechanism for trim mower cutting units

ABSTRACT

A shift mechanism for trim mower cutting units includes a pair of slidable carriers. Each slidable carrier can slide along a pair of guide rods mounted to a mower frame. A hydraulic extension cylinder is connected to each slidable carrier and independently extends to move the slidable carrier laterally outward from the mower frame or retracts to move the slidable carrier laterally inward in relation to the mower frame. A hydraulic shifting cylinder is mounted between the two extension cylinders and extends to shift both slidable carriers laterally inward toward a center position, and retracts to move both slidable carriers laterally outward toward an extended position.

FIELD OF THE INVENTION

This invention relates generally to grass mowing machines, andparticularly to trim mowers used to cut grass on small or enclosed roughand fringe areas, and around bunkers and sand traps of golf courses.

BACKGROUND OF THE INVENTION

Trim mowers, also sometimes referred to as utility mowers, may be usedto mow the smaller and/or enclosed rough and fringe areas on golfcourses. These areas may require a trim mower having a relatively narrowcut width because the areas may include undulating terrain, or may betoo small or confined for larger mowing machines. Trim mowers mayinclude three cutting units powered by and attached to a tractionvehicle. For example, two front cutting units may be positioned forwardof the vehicle's front pair of wheels, and a rear cutting unit may bebetween the front wheels and a single rear wheel used for steering. Therear cutting unit may cut a swath between the two front cutting unitsthat overlaps the swaths cut by the two front cutting units.

Trim mowers have a tendency to “crab” when operated on side slopes thathave relatively steep inclines or undulations that are common on manygolf courses. Crabbing refers to the rear wheel tracking or slidingdownhill from the centerline of the trim mower. Crabbing may cause thetrim mower to leave uncut strips of grass. This occurs when the rearcutting unit tracks or slides downhill so much that it no longer canoverlap the two front cutting units.

To prevent or minimize uncut strips, trim mowers may be designed withadditional overlap between the front and rear cutting units. However,greater overlap also can reduce a trim mower's cutting width, resultingin lower productivity of the trim mower in flatter areas. A trim moweris needed having high versatility, and that will prevent or minimizeuncut strips without sacrificing productivity.

When trim mowers are used to cut grass at or near the edge of a golfcourse hazard such as a sand trap or bunker, or other golf coursefeature, the machine's weight may cause the bunker wall to collapse,especially in sandy soil conditions. Additionally, a trim mower weighing1000 pounds or more may slide into a sand trap or bunker, get stuck,become high centered, or experience reduced stability. A trim mower isneeded that will reduce the risk of damage to golf course features suchas sand traps or bunkers. A trim mower is needed that will maintainstability and minimize the risk of sliding into a sand trap or bunker,becoming high centered or stuck.

Efforts have been made to design and make trim mowers that solve one ormore of these problems. For example, U.S. Pat. Nos. 6,032,441 and6,351,929 relate to a triplex trim mower with a pair of laterallyadjustable cutting units. The cutting units are supported by a lateralcarrier frame which is slidably engaged to a lateral support frame. Ahydraulic cylinder permits the carrier frame to be laterally displacedwith respect to the vehicle frame to reach the edge of a bunker or sandtrap while the machine maintains a distance from that feature. Whentrimming around an obstacle on a slope with the cutting units shifted tothe downhill side, the trim mower may experience reduced stabilitybecause all cutting units are shifted by a single carrier which supportsits own weight along with weight of the cylinders and lift arms. Whenthis weight and the cutting units are shifted to the downhill side, thecenter of gravity of the machine is moved into a less favorable positionthat can lead to reduced stability. If both cutting units are shifted toone side of the machine with the single carrier frame, the opposite sidetire may roll on uncut turf, resulting in poor cut quality and anunsightly cut pattern.

A shift mechanism for a trim mower cutting units is needed thatminimizes the reduction of stability when one or more cutting units areshifted and extended outwardly, especially while the machine is on steepslopes. A shift mechanism is needed that will minimize the shift in thevehicle's center of gravity if one or more cutting units are extendedoutwardly. A shift mechanism is needed that will not cause the uphilltire to roll on uncut turf, and that will help a trim mower achieve abetter cut quality and cut pattern.

Shift mechanisms have been proposed to move cutting units laterallyoutwardly. For example, U.S. Pat. No. 2,882,978 relates to a selectablyslidable, laterally offset mower for trimming beneath overhangingobstacles such as low tree branches. U.S. Pat. No. 4,873,818 relates toa similar mower that provides increased offset capability. U.S. Pat.Nos. 4,893,456 and 5,483,789 relate to single cutting decks that can belaterally displaced from a conventional centered position to a laterallyextended position. These devices are not well suited and have not beenadapted for use on trim mowers that are used to cut rough and fringeareas on a golf course.

A shift mechanism for a trim mower is needed that allows a cutting unitto reach and mow grass in small or enclosed areas of golf courses,especially around the edges of hazards such as sand traps and bunkers,but that will not sacrifice productivity when mowing other areas. Ashift mechanism for a trim mower is needed that is capable of increasingthe mower's cutting width, or increasing the overlap between front andrear cutting units. A shift mechanism for a trim mower is needed thathelps the vehicle maintain stability when mowing on side hills, or if acutting unit is moved laterally. A shift mechanism is needed that canreduce the risk of damage to the edges of sand traps and bunkers.

SUMMARY OF THE INVENTION

A shift mechanism is provided for trim mower cutting units, that allowseach cutting unit to mow grass in small or enclosed areas of golfcourses, especially around the edges of hazards such as sand traps andbunkers, but that will not sacrifice productivity when mowing otherareas. The shift mechanism is capable of increasing the mower's cuttingwidth, or increasing the overlap between front and rear cutting units.The shift mechanism also helps reduce the loss of vehicle stability whenmowing on side hills or hazards while a cutting unit is moved laterally.The shift mechanism can reduce the risk of damage to the edges of sandtraps and bunkers.

The shift mechanism includes a pair of slidable carriers. Each slidablecarrier can slide along a pair of guide rods mounted to a mower frame. Ahydraulic extension cylinders is connected to each of the slidablecarriers and independently extends to move the slidable carrierlaterally outward from the mower frame or retracts to move the slidablecarrier laterally inward in relation to the mower frame. A hydraulicshifting cylinder is mounted between the two extension cylinders andextends to shift both slidable carriers laterally inward toward a centerposition, and retracts to move both slidable carriers laterally outwardtoward an extended position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a rear perspective view of cutting units that may be used on atrim mower having a shift mechanism for trim mower cutting units in afirst embodiment of the invention.

FIG. 2 is a rear view of view of a shift mechanism for trim mowercutting units in a first embodiment of the invention.

FIG. 3 a front perspective view of a shift mechanism for trim mowercutting units in a first embodiment of the invention.

FIG. 4 is a schematic of a hydraulic system for the shift mechanism fortrim mower cutting units in a first embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIGS. 1-3, in one embodiment of the invention, shiftmechanism 10 may be provided on a self-propelled trim mower having threeseparate cutting units 11, 12, 13. For example, the self propelled trimmower may include a frame supported by left and right front drivewheels, a steerable rear wheel, an engine compartment arranged on aframe over and/or slightly forward of the rear wheel. The shiftmechanism of the present invention, however, may be employed on varioustypes and configurations of mowing vehicles other than trim mowers.

In one embodiment, cutting units 11, 12, 13 may be hydraulically orelectrically powered. For example, as shown in FIGS. 1-3, each cuttingunit may be a mower deck covering a rotary cutting blade. Alternatively,each cutting unit may be a reel-type cutting unit with a horizontallyaligned reel that cuts the grass between a spiral blade and bedknife.

In one embodiment, shift mechanism 10 is used for two front cuttingunits 11, 12 pivotably mounted to lift arms 14, 15. Each of the frontlift arms 14, 15 is mounted to a separate slidable carrier 17, 18. Eachslidable carrier 17, 18 can traverse laterally, relative to the trimmower, along parallel guide rods 19, 20. The ends of guide rods 19, 20are mounted to the mower frame with brackets 33, 34. Rear cutting unit13 may be pivotably attached by lift arm 16 to the frame of the trimmower.

In one embodiment, each slidable carrier 17, 18 may slide along the pairof guide rods 19, 20 to extend or retract a front lift arm 14, 15 andthe attached front cutting unit to a lateral position relative to thetrim mower. An extended lateral position may be preferred for hill sidemowing or undulating ground, and/or provide optimal overlap between thefront and rear cutting units. Each slidable carrier 17, 18 may positiona front cutting unit at an outward offset position, relative to the trimmower, to allow mowing around obstacles on golf courses.

In one embodiment, shift mechanism 10 may include a pair of hydrauliccylinders 21, 22 referred to as extension cylinders. The first extensioncylinder 21 may be attached to slidable carrier 17 by its rod end 23,and to a frame mounted bracket at its base end 24. The second extensioncylinder 22 may be attached to slidable carrier 18 by its rod end 25,and to a frame mounted bracket at its base end 26. The two extensioncylinders 21, 22 may be mounted laterally on the trim mower, with oneover the other.

In one embodiment, shift mechanism 10 also may include a third hydrauliccylinder 27 referred to as the shifting cylinder. Shifting cylinder 27may be mounted between the two extension cylinder bodies. The rod end 28of the shifting cylinder may be attached to the body of extensioncylinder 21, and the base end 29 of the shifting cylinder may beattached to extension cylinder 22. The shifting cylinder also may beoriented laterally with respect to the trim mower, and vertically inline between the extension cylinders.

In one embodiment of the invention, hydraulic lift cylinders 31, 32 maybe mounted between slidable carriers 17, 18 and the respective lift armsto raise front cutting units 11, 12 into a transport position, or lowerthe front cutting units into a mowing position. Rear cutting unit 13 maybe raised or lowered using hydraulic lift cylinder 35.

In one embodiment, to position front cutting units 11, 12 to providemaximum overlap and prevent uncut strips of grass, shifting cylinder 27may be fully extended to pull slidable carriers 17, 18 to a centerposition relative to the trim mower. To position front cutting units 11,12 for maximum productivity, shifting cylinder 27 may be fully retractedto move the slidable carriers equally outward laterally relative to thetrim mower, to an extended position. To position one of the frontcutting units further outward laterally from the trim mower (to reachthe edge of an obstacle such as a sand trap, for example) than the othercutting unit, the extension cylinder for that cutting unit may beextended. The extension function may be controlled proportionally toallow the operator to extend the respective cutting unit to a desireddistance outside of the trim mower's front tire, up to a maximum point.

FIG. 4 shows an embodiment of a hydraulic circuit that may be used forshift mechanism 10. The hydraulic circuit includes shifting valve 36with valves SV1-SV4, and lift valve 37 with valves LV1 and LV2. Shiftingvalve 36 may be an electro-hydraulic control valve 36 that independentlycontrols movement of extension cylinders 21, 22 and shifting cylinder27. Lift valve 37 may also be an electro-hydraulic control valve thatcontrols movement of lifting cylinders 31, 32 and 35. Lift valve 37 maybe hydraulically plumbed in series with shifting valve 36 so thathydraulic flow enters the shifting valve first, and exits the shiftingvalve before entering the lift valve.

In one embodiment, the hydraulic circuit of FIG. 4 prevents the operatorfrom raising cutting units 11, 12 if they are in an extended positionthat could be unstable. When raising cutting units 11, 12, valve LV1 inlift valve 37 is activated to block flow through the valve. Thisshifting operation builds pressure in the hydraulic lines to the liftcylinders, and to the rod ends of the extension cylinders. It requiresless pressure to retract an extension cylinder than it does to lift acutting unit, so the extension cylinder will retract first and pull therespective cutting unit to its inward position. Once the extensioncylinder is fully retracted, the cutting unit has reached its inwardposition, and the hydraulic pressure will continue to increase enough toraise all of the cutting units. The hydraulic circuit assures thecutting units will always be in a retracted position prior to raisingthem to a transport height.

In one embodiment, to operate the shifting function to move the cuttingunits into a maximum overlap or maximum productivity position, valve SV1is activated to block flow through shifting valve 36 and build hydraulicpressure. SV4 of the shifting valve is then activated in one directionor the other to apply the built pressure to the shifting cylinder tomove the cylinder into a fully retracted or fully extended position.

In one embodiment, to operate the cutting extension function, valve SV1of the shifting valve is activated to block flow through the shiftingvalve and build hydraulic pressure. SV2 or SV3 of the shifting valve isthen activated, depending on which cutting unit extension is desired, todirect the pressurized fluid to the base end of the cylinder. Thepressurized fluid causes the respective extension cylinder to extend andmove the cutting unit to an outward position. This extension may becontrolled proportionally by activating or releasing a control inputapparatus such as a lever or button.

The shift mechanism according to one embodiment of the invention allowsa trim mower to cut rough or other confined areas on golf courses withcutting units that are remotely movable by the operator as needed, whileminimizing any change of the center of gravity of the mower. The shiftmechanism can maximize productivity of a mower by moving the cuttingunits into a position that can provide a maximum width of cut. The shiftmechanism can reduce the chance of uncut strips due to crabbing duringhillside mowing, by moving the cutting units to a maximum overlapposition. The shift mechanism can also move the cutting units betweenthe maximum overlap and maximum width of cut positions. The shiftmechanism allows the operator to extend a cutting unit out to one sidefor trimming around obstacles or golf course hazards. The shiftmechanism prevents raising the cutting units if they are extendedlaterally outwardly from the vehicle.

Having described the preferred embodiment, it will become apparent thatvarious modifications can be made without departing from the scope ofthe invention as defined in the accompanying claims.

1. A shift mechanism for trim mower cutting units comprising: a pair oflift arms, each lift arm mounted to a separate slidable carrier, eachslidable carrier can slide along a pair of guide rods mounted to a mowerframe; a pair of hydraulic extension cylinders, each extension cylinderconnected to one of the slidable carriers and independently extending tomove the slidable carrier laterally outward from the mower frame orretracting to move the slidable carrier laterally inward in relation tothe mower frame; and a hydraulic shifting cylinder mounted between thetwo extension cylinders and extendable to shift both slidable carrierslaterally inward toward a center position, and retractable to move bothslidable carriers laterally outward toward an extended position.
 2. Theshift mechanism of claim 1 further comprising a pair of hydraulic liftcylinders, each lift cylinder connected to one of the lift arms to raiseand lower the lift arm.
 3. The shift mechanism of claim 2 furthercomprising a hydraulic circuit that actuates the extension cylinders toretract the lift arms before actuating the lift cylinders to raise thelift arms.
 4. The shift mechanism of claim 3 wherein the hydrauliccircuit includes a lift valve to raise and lower the lift arms in serieswith a shifting valve to extend and retract the lift arms.